It is known to roughen the surface of implants. Various approaches have been suggested, each producing a unique surface. One approach has been to apply materials to the surface of the implant such as, for example hydroxyapitite, a material that is considered also to improve the bonding of the implant to bone because the hydroxyapitite is chemically related to bone. In a related approach, titanium particles have been sprayed onto a titanium implant to roughen the surface. Roughening can also be done by removing some of the surface. Grit blasting with fine particles has been proposed to create dents and to abrade away some of the surface.
Another method is the use of acid etching to create a roughened surface. At least one supplier of dental implants has proposed grit blasting to create a coarse roughened surface, followed by acid etching to form a superimposed fine roughening. In a series of U.S. patents, including U.S. Pat. Nos. 5,603,338, 5,876,453, 5,863,201, assigned to Implant Innovations Inc., a unique two-step acid treatment was disclosed and is used on dental implants having an Osseotite® surface. The first acid treatment used aqueous hydrofluoric acid to remove the “native oxide”, which is the titanium oxide found on titanium metal surfaces. Removing the native oxide is important since it makes the metal surface more easily accessible to etching by other acids that are otherwise unable to uniformly etch the surface of titanium containing native oxide. The second acid treatment desirably used a mixture of hydrochloric and sulfuric acids to etch the exposed titanium surface. A relatively fine etching was achieved, having peak-to-valley heights of 10 microns or less. The peak-to-peak distance typically is about from about 1 to about 3 microns. This Osseotite® surface has achieved commercial success, having reduced the time required for osseointegration of the titanium implant with bone.
Previous U.S. patents have shown the titanium surface obtained by scanning electron microscopy (SEM). Another method of describing the surface is surface mapping microscopy (SMM), which produces a computer-generated three-dimensional picture of the region being examined, and several calculated measures of the roughness of the surface. It will be understood by those skilled in the art that acid treatment produces a surface that appears very uniform to the naked eye, but contains variations that become evident only when greatly magnified, as in the photomicrographs. Each region will not be precisely the same as the others, but nevertheless, the variations are small and fall within the general limits discussed above. By carefully controlling the treatment process, each implant has substantially the same surface.
It would be desirable to improve and simplify existing processes, while still producing a desirable uniform surface.